Blooms of the toxic dinoflagellate, Karenia brevis, are a frequent occurrence off the coast of Florida in the Gulf of Mexico. Although such blooms generally develop and terminate offshore, wind and currents can concentrate assemblages in nearshore waters, creating a condition referred to locally and elsewhere as “red tide”. Harmful algal blooms pose a threat and efforts to reduce or eliminate their negative impacts and consequences are necessary. In the Gulf of Mexico, toxic blooms of K. brevis regularly lead to untimely restrictions on commercial and recreational shellfish harvesting and deleterious effects on tourism and public health. Toxic blooms of K. brevis are generally detected by visual confirmation (e.g., water discoloration and fish kills), illness to shellfish consumers, or human respiratory irritation with actual toxicity verified through time-consuming chemical analyses for brevetoxins within shellfish samples and mouse bioassays. Currently, biological monitoring programs primarily rely on microscope-based cell enumeration and gross measurements of a biochemical parameter, such as chlorophyll-a concentration, for characterizing algal species and estimating biomass. Existing methods can be slow, labor intensive, intermittent, and do not always provide timely or accurate measurements. Developing optical detection methods for discriminating particular phytoplankton species in mixed phytoplankton assemblages has long been a goal of aquatic scientists. Phytoplankton pigment and light absorbance analyses could be incorporated into coastal monitoring programs and thus provide an effective and alternative means for monitoring K. brevis. Mitigation of some of the harmful effects resulting from toxic blooms of K. brevis could be achieved by early detection of this species in mixed phytoplankton communities.
The majority of organic carbon in the oceans is present as dissolved organic matter (“DOM”). A significant proportion of DOM has color (abbreviated “CDOM”), and is often present in concentrations sufficient to affect the color of lakes, estuaries, and near-shore coastal water. Due to the presence of CDOM in waters where phytoplankton assemblages occur, baseline CDOM measurements of water in the area are necessary. Additionally, mapping the distribution of CDOM including its time-space variability is central to understanding global carbon cycles. Characterizing CDOM variability is problematic because standard spectrometric methods for determining CDOM concentration are laborious and susceptible to methodological biases. For example, the collection and storage of discrete water samples for analysis in the laboratory often introduces artifacts such as contamination and photolysis. Also, the numerous steps required to conduct these analyses limit the number of samples that can be collected and effectively analyzed.
The use of liquid waveguide capillary cell (“LWCC”) technology for CDOM absorption measurements has been described in E. J. D’Sa et al., “Determining optical absorption of colored dissolved organic matter in seawater with a liquid capillary waveguide”, Limnol. Oceanogr. 44, 1142–1148 (1999). A near-continuous automated LWCC analytical technique for mapping CDOM distribution in an aquatic system is described in Kirkpatrick et al., “Continuous hyperspectral absorption measurements of colored dissolved organic material in aquatic systems”, Applied Optics, 42, 33, 6564–68 (20 Nov. 2003). Devices employing an LWCC are also described in U.S. Pat. Nos. 6,020,207 and 6,603,556 B2.